China produces 99% pure graphene for quantum chips.

A research team at Peking University has developed a more efficient method for producing rhombic graphene, paving the way for the production of next-generation quantum computers with better noise immunity.

According to Interesting Engineering, researchers at Peking University have developed a method for producing a special graphene-based material that could make quantum computers more widespread in the future. According to research published in the journal Science, scientist Liu Kaihui and colleagues have overcome a major hurdle to create rhombic graphene with unprecedented purity and size. This type of graphene is highly valued for its ability to contain multiple quantum states while maintaining stability.

Rhombic graphene is a multilayered graphene with an ABCABC stacking order (instead of the common ABAB type), creating rhombic symmetry. In this arrangement, the layers shift in the same direction before repeating, but the structure is less stable due to its tendency to decay into the ABAB type. The rhombohedral layered structure creates a flat energy band that promotes strong electron interaction and good anti-interference, overcoming one of the main obstacles of quantum computing.

According to Zhang Zhibin, co-author of the study, previously, the only way to obtain rhombohedral graphene was through manual peeling. Researchers had to separate graphite with adhesive tape and examine the fragments under a microscope until they found a fragment with the correct arrangement (which accounts for less than 1% of the sample).

Rhombohedral graphene. Image: University of Texas Dallas

However, the new manufacturing method can create ABC sheets in a controlled process. According to SCMP, the research team used an aluminum oxide surface, then added a copper-nickel alloy as a catalyst and a mold. They used high temperatures to assemble carbon into graphene and further manipulated it to fix the consecutive layers in the ABC chain. The result is a sample with 99% purity, a maximum size of 160 x 80 micrometers, and a thickness of up to 120 nanometers. Researchers can also adjust the number of layers from a few dozen to several hundred as needed.

Liu Kaihui explained that the new material could provide an excellent platform for producing graphene-based quantum chips. He said that integrating 2D materials into the most power-consuming parts of AI chips or the highest-density areas in memory chips is attracting much attention.

In the future, the research team plans to assemble these small rhombohedral graphene fragments to produce larger sheets, ready for use in devices.